Progress made in the field of prosthetic denistry during the last century, combined with constantly increasing longevity of the population and the rise in the standard of living, have contributed greatly to the popularity and increased utilization of permanent dental prothesis. With this came the need for a cost effective, esthetically acceptable and reliable method for restoring fractured or worn veneers made of porcelain or acrylic.type resins. These materials are more fragile and/or softer than the durable metal base of the cast restoration. Therefore, they are more susceptible to fracture and/or wear.
The in situ repair of damaged or worn restorations was, up to now, virtually impossible. applying a layer consisting of a copolymer of acrylic or methacrylic acid and a copolymerizable monomer over the metal base of the restoration, followed by the application of a conventional resih based dental restorative. The intermediate layer provides good bonding strength, both to metal and restoratives, thus assuring durability of the restoration. Illustrative resin based dental restoratives are set forth in Lee U.S. Pat. No. 4,107,845, Waknine U.S. Pat. No. 4,544,359, Waknine U.S. Pat. No. 4,547,531, and Bowen U.S. Pat. No. 3,066,112. The entire disclosures of these patents are hereby incorporated by reference and relied upon.
By copolymerizing acrylic or methacrylic acid with another monomer, insolubility in oral fluids is achieved, while preserving the good adhesive properties of polyacids. The presence of ethylenically unsaturated groups in the primer, combined with its limited chemical resistance to acrylic or methacrylic resins (present in the restorative) assures a good bond between the primer and the restorative, enhanced by the copolymerization in the interface layer.